The proposed research will assess the model that affective disturbances of infants and young children develop in the context of an interactive relationship with the mother (caregiver). The mother serves as a modulator, providing adequate stimulation and arousal modulation necessary for the development of organized behavioral patterns and physiological rhythms. If the mother is affectively unavailable (as in maternal depression or maternal deprivation syndrome) or physically unavailable (as in maternal separation), behavioral and physiological disorganization will occur, manifested by asynchrony in the mothers' and infants' rhythms and by disturbances in affective and vegetative functions. Maternal deprivation effects will be studied in several samples including infants of depressed mothers (prepartum, postpartum and prepartum/postpartum depression) and non-organic failure-to-thrive infants of depriving mothers as compared to normal mothers and infants. The maternal separation groups will include: a. infants/young children separated for hospitalization; b. separation surrounding mothers' conference travel; and repeated separations related to c. commuter parenting and d. joint custody. These situations will be studied in a repeated measures design (baseline/separation/reunion). The coherence/synchrony of affective behavior, activity level and heart rate rhythms of these mothers and infants will be investigated in the context of their early interactions. The generalizability of the infants' affective disturbances across interaction partners and the emergence and chronicity of the disturbance will be determined in a longitudinal design. Changes in vegetative functions will be monitored including changes in sleep cycles, eating, elimination and illness. Biochemical activity will be assayed including catecholamines and their metabolites (NE,E,MHPG,VMA), cortisol and growth hormone. Finally, individual differences in the mothers' and infants' affective styles (externalizer/internalizer), temperament and coping styles (active/passive) will be investigated. This research will hopefully provide a model for the psychophysiology of early affective disturbances and enhance our understanding of the neurohormonal mechanisms underlying affective disturbances in infants and young children experiencing maternal depression, deprivation and separation.